The invention concerns a picker line as is used for the transposition of individual products into deposit groups which can accommodate a given number of individual products. In the following instead of the term deposit group the term container is used. The term container here is to be understood less than such as a container, but rather as individual products or a group of individual products that after the transposition by the pickers are placed in a defined position relative to a transportation device and possibly in a defined position within the group of individual products.
The procedure usually involved is such that the individual products are delivered on a product conveyor belt and the containers are delivered on a container conveyor belt and that both the individual products and the containers are transported alongside the pickers which are located in fixed positions. The container conveyor belt can be a transportation device that introduces containers or placing positions with a Cartesian coordinate, either in fixed or variable distance but stationary relative to the transportation device. Container conveyor belts also can be formed by thermoform machines or feeding chains that contain cavities, containers or drivers in fixed, or variable according to the indexing of the belt, distance.
From the perspective of a central control system or the individual controls of each picker of such a picker line, there is no difference whether it concerns containers or cavities or Cartesian placing positions.
In practice, the containers are delivered predominantly on a first transportation device and generally accumulated thereon. Then the containers are transferred from the first transportation device onto a second transportation device, the effective container conveyor belt, on which the respective containers are filled with the appropriate number of individual products, and then, after complete filling of each container, the containers are in turn passed onto a third transportation device for the filled containers to be transported away. However in case of containers or cavities that are stationary relative to the container conveyor belt, in particular cavities of a thermoformer or infeed chains of a flow wrapper, the delivery, filling and removal of the containers is carried out with one transportation device.
DE 42,08,818 C2 discloses a picking line where the pickers are not located in a fixed position relative to the product conveyor or container conveyor but are limitedly and jointly movable in running direction of the conveyors and which are individually movable in orthogonal direction of the conveyors. Thereby the picking of the individual products, and the placing of the individual products into a container can be performed with a moving product conveyor and container conveyor. At the most the product conveyor feeding individual products may be temporarily stopped. This complicates the coupling to a continuously producing production machine for individual products, and only one picker can pick or place a product and not both pickers together. Furthermore there is no advantage visible from the shown arrangement of the product conveyor in cocurrent or concurrent direction.
In contrast, EP 0,749,902 B1 discloses a picker line with which the individual products are counted at the entrance to the picker line in order to release a new container to container conveyor belt when the number of products required to fill a container is achieved. Further it is disclosed that the container conveyor belt and the product conveyor belt are advanced in cocurrent manner or that the container conveyor and the product conveyor are realized as one joint conveyor. It has proved to be particularly problematic that it cannot be ensured that all containers are completely filled when the products are delivered irregularly or on narrow product conveyor belts.
Both documents WO 2004/113030 A1 and EP 1,285,851 A1 seize these problems and disclose a picker line where the individual products also are counted at the entrance of the picker line and where each counted individual product is assigned to a container or a placing position by means of mathematical optimization for loading by a determined picker in the picker line. Such a discrete loading optimization in practice proves to be computation intensive and can likewise not ensure the complete filling of containers in case of irregular or relative to the filling positions per container lower infeed of individual products.
This problem of incomplete filling is raised in DE 29817239 U as well as in EP 1,352,831 B1 where in each case an intermediary buffering of individual products is proposed, which individual products can be utilized for the complete filling of containers. It is however disadvantageous, that the performance for buffering and extracting individual products by means of one or more pickers into and from an intermediary buffer is to be deducted from the overall performance of the picker line.
Further comparable systems are known from EP 1,160,166 B1 for the simultaneous handling of upright and recumbent individual products, and from FR 2754239 A1 regarding separate product conveyors for different individual products. None of these systems does propose a new approach regarding the problem statement that was indicated at the outset.
A further generic method is disclosed in EP-A-0 856 465. There, individual products and containers are guided on parallel transportation devices for the individual products and for the containers along a picker line in countercurrent. In case of single or multiple intersections of the transportation devices, the running direction of the product transportation device and of the container transportation device is likewise chosen such as to maintain the countercurrent mode of action. Thereby the relative speed of the irregularly supplied products in relation to the supply of containers, but also the delivery of the next container to be filled is controlled by the controller of the last, or in case of failure the last but one, picker in such a manner that only completely filled containers leave the work area of this last picker. Thereby both the gripping of individual products and the placing of individual products are realized, as shown in DE 42 08 818, by synchronizing the picker to the moving product conveyor or container conveyor. EP 0,856,465 B1 further describes that no individual products should leave the work area of the last picker in direction of the individual product flow. The summary of the invention of EP 0,856,465 B1 discloses several methods of how this is being achieved. Paragraph 61 and 62 describe that the controller of the last picker in moving direction of the container belt, or in case of breakdown of this last picker the last but one picker reduces the speed of the container transportation device if otherwise an incompletely filled container would be discharged from the working area of this last or last-but-one picker. Paragraph then describes that thereby the containers located in the workarea of the preceding pickers are being filled to a higher level or even completely by these preceding pickers. Since the performance of all pickers can be used up to the entire filling of the containers in case of a reduced speed setting of the container transportation device, it can be ensured that no unhandled individual products leave the transposition area of the picker line.
Further it is known from EP 0,856,465 B1 that the described principle can be realized with only a single picker what is often the case with a correspondingly low quantity of individual products to be transposed into containers.
U.S. Pat. No. 6,122,895 and EP 0,856,465 B1 disclose further potential characterizing features. In particular a method is described, by which the delivery of the next container to be filled into the work area of the pickers is dependent on the supply of the required number of individual products.
In summary a picker line according to EP 0,856,465 B1 concerns a combination of several, as required by the number of supplied individual products, additionally required pickers which load as many individual products as possible up to their entire filling into containers and an individually working last or in case of failure of the last an individually working last-but-one picker whose task it is to completely fill containers and to discharge the container after complete filling and to deliver a next container to be filled into the picker line.
This method is particularly suitable for picker lines where the supply of individual products is often completely interrupted and where the product transportation device cannot be stopped or at least decelerated in area of the picker line. It then is required that all pickers transfer as many individual products as possible since due to the complete interruption of the supply of individual products the container transportation device remains in stoppage since no completely filled containers can be discharged from the working area of the last picker, but still in the rear area of the picker line individual products have to be transferred into containers. As soon as individual products are supplied on the product conveyor again, this subsequently results in an unavoidable accelerated motion of the container transportation device, since the last picker in running direction of the container transportation device cannot operate as no or just some isolated loading positions are available in the completely or almost completely filled containers.
This method proves to be unfavorable when the delivery of individual products by the majority just fluctuates or if in case of a complete interruption the product transportation device can be brought to a complete stop in the transposition area of the pickers, which is typically the case. In such cases an excessive utilization of the pickers within certain areas of the picker line and considerably larger speed fluctuations of the container transportation device may result even though the fluctuation in the delivery of individual products would not necessitate this. It is further disadvantageous that while transposing different types of individual products the method requires a sophisticated tuning of the relative speed of the container conveyor belt and of the product conveyor belt for each type of individual product in order to ensure a uniform workload for each picker.
In practice the application of this method still often requires to control the complete filling of the containers after discharging the containers from the transposition area of the picker line. Even though the last picker by means of the control system does ensure that all containers are completely filled, it is from a practical view obvious, that certain individual products are not accurately picked, are damaged during gripping or are not precisely placed in the container. Accordingly it can be assumed that the aim of the complete filling of containers according to this method is theoretically achieved, but in practice an individual inspection is required.
Finally EP 1,226,408 B1 discloses a system with at least two pickers, which system allows forming weight determined containers based on a weight determination of each individually handled product.
EP 1,819,994 B1 proposes a method and a system to form weight determined groups or containers, whereby these groups or containers can be discharged by means of several transportation devices. A particular characteristic is to form different groups of individual products on different transportation devices in order to increase the efficiency of the system. This method proves to be disadvantageous when similar groups or containers have to be formed and where it is required to ensure that all individual products are handled without renewed feeding of not completely filled groups or containers.
EP 0,781,172 B1 does not directly address the weight determined loading by means of a picker line, but presents a method to predetermine the probability that a container can be completely filled based on historical weights of individual products. Thereby it is shown that numerous available individual products are critical for the complete filling of a container.
It is therefore an objective of the present invention to provide a method and an apparatus by means of which a picker line in countercurrent operation mode allows to transfer individual products in containers, such as blisters on a transportation device, cavities of a grouping chain, stacks of individual products transferred by engaged pushers of a grouping chain or deep drawn moulds of a thermoform machine as regularly as possible and which permits an improved efficiency and a balanced operation of the picker line without significantly increasing the effort required to handle the containers to be filled.
This objective is achieved by a method and an apparatus having the features of patent claim 1 and 16, respectively.